Hybrid electric vehicles (HEV) or Extended-Range Electric Vehicles (EREV) typically include an internal combustion engine and an electric motor which are operable to drive the vehicle. When a driver of the vehicle depresses an accelerator pedal, a control module establishes a driver power command and thereafter controls the engine and/or the electric motor to meet such command.
In a series HEV, the motor provides the primary source of propulsion while the internal combustion engine drives an electric generator. The electric generator both charges batteries in the vehicle and powers the electric motor.
The usage of the internal combustion engine is dependent on the charge of the batteries. In some cases, the internal combustion engine is only used after, for example, so many hours of consecutive use. It is possible for those who only drive short distances to never or very rarely make use of the internal combustion engine in the HEV.
In such cases, stored fuel for the internal combustion engine remains unused for extended periods of time. Storing fuel over an extended period of time can result in deposits in the fuel system, due to the oxidation of the fuel. The deposits can prevent proper operation of the engine.